1. Field of the Invention
The present invention relates to a liquid crystal display device, and specifically to a liquid crystal display device having a transparent front plate attached to an image display surface.
2. Description of the Related Art
In a liquid crystal display device using liquid crystal, light from a light source is recognized as an image after having passed through a liquid crystal layer, a color filter, a polarizing plate, and so forth.
In the above, a polarizing plate is used for the forefront surface of a liquid crystal display device used for a monitor of a personal computer or a liquid crystal television, and an anti-glare (AG) film having fine concaves and convexes formed thereon or a reflection preventing film is attached to the surface of the polarizing plate in order to suppress reflection on the surface. Some liquid crystal panels employ a glass plate having thickness of approximately 0.5 to 0.7 mm mounted under the polarizing plate.
A liquid crystal display device used in a portable phone is constantly placed under a state of being rubbed as the portable phone is often carried in a pocket of clothes. As such a use is expected, an image display surface has a structure in which a transparent substrate, such as acrylic resin, or the like, is attached to the polarizing plate so that the clothes, or the like, do not directly touch the image display surface.
As the thickness of the glass plate under the polarizing plate of a personal computer monitor or a liquid crystal television is of approximately 0.5 to 0.7 mm, as above-described, the glass plate may possibly be broken when being bumped by a dish, a vase, a toy, or the like, with significant impact.
In the trend of enlarging the size of the screen of a personal computer monitor and a liquid crystal television, there is an increasing possibility of breaking the glass plate even with very small impact as shockproof performance of the glass plate will decrease as the screen size becomes larger while the glass plate thickness remains unchanged.
To address the above, there is proposed a method for improving shockproof performance by providing a transparent substrate (hereinafter referred to as a front plate) to the forefront surface, similar to a portable phone.
However, as there is a gap between the front plate and the polarizing plate, significant reflection of ambient scenery on the image display surface is caused due to reflection by three surfaces, namely, the front and back surfaces of the front plate and the surface of the polarizing plate. This results in deterioration of visibility in a bright place.
To address the above, Patent Documents mentioned below disclose a method for suppressing reflection by the polarizing plate and that by the front plate on the polarizing plate side by filling transparent organic medium in the gap between the front plate and the polarizing plate.    Patent Document 1: Japanese Patent Laid-open Publication No. 11-174417    Patent Document 2: Japanese Patent Laid-open Publication No. 6-75210    Patent Document 3: Japanese Patent Laid-open Publication No. 9-318932    Patent Document 4: Japanese Patent Laid-open Publication No. 5-165011    Patent Document 5: Japanese Patent Laid-open Publication No. 7-64066
Here, when the front plate is made of glass, the front plate needs a protection film attached thereto in order to prevent the glass from being scattered should the glass be broken due to impact. In addition, provision of an anti-glare layer or an anti-reflecting layer on the film is desired in order to prevent deterioration of visibility of an image due to reflection of ambient scenery.
The protection film, however, produces a waste of a separate film for protecting the adhesive layer, which resultantly places a burden on the environment.
Moreover, as a transparent organic medium layer, a front plate, and a protection film are provided in addition to a conventional liquid crystal panel, visibility may be deteriorated unless these layers are attached without causing bubbles. This leads to decrease of yield, and thus increase of the ratio of a liquid crystal panel to be disposed of. This resultantly places a further burden on the environment.
Moreover, even if the layers can be attached without causing bubbles, an increase of the number of interfaces results in accumulated reflections though reflection on each interface is small, which results in a darker screen image when the same backlight is used.
To address the problem, it is necessary to increase the amount of light emitting from the backlight. This leads to increase of power consumption, which again places a further burden on the environment.